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ŠUMARSKI LIST 7-8/2014 str. 37     <-- 37 -->        PDF

In both years the greatest number of larvae developed during the period from the beginning of the third decade of April till the end of the second decade of May, but outside this range a small number of larvae were present, hence the greatest damages caused by larvae occurred in this period.
Laboratory studies revealed that ash weevil larvae undergo three developmental stages. Average larval development of the first stage lasted for 6.4 days, while larvae of the second and the third stage had shorter developmental time (5.1 i.e. 5.8 days). It was determined that larval development lasted between 16 and 20 days (on average 17.3 days). Larvae of the first stage damaged leaf insignificantly, and on average consumed 0.24cm2 of leaf area. Second stage larvae consumed on average 0.65cm2, and that of third stage 2.41cm2. The sexual ratio index of 40 grown larvae was 18/22 (female/male). Females larvae consumed larger leaf area compared to male larvae. On average male larvae consumed 3.02 cm², and females 3.63 cm² of narrow – leaved ash leaf. It was determined that both sexes consumed on average 3.3cm2 of leaf area during larval development.
Upon completion of development larvae secrete slimy layer, which dries and hardens after several hours forming a cocoon. They first enter the pre-pupa stage without molting and then transform into the pupa. Pre-pupa stage last for two days. Pupa stage lasts between 6 and 8 days (on average 7 days)